Cycling and persistence of iron-bound organic carbon in subseafloor sediments.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39075044.
- Also identified by DOI 10.1038/s41467-024-50578-5 and PMC identifier 11286938.
- Licence recorded as CC BY-NC-ND.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
Reactive iron (Fe<sub>R</sub>) serves as an important sink of organic carbon (OC) in marine surface sediments, which preserves approximately 20% of total OC (TOC) as reactive iron-bound OC (Fe<sub>R</sub>-OC). However, the fate of Fe<sub>R</sub>-OC in subseafloor sediments and its availability to microorganisms, remain undetermined. Here, we reconstructed continuous Fe<sub>R</sub>-OC records in two sediment cores of the northern South China Sea encompassing the suboxic to methanic biogeochemical zones and reaching a maximum age of ~100 kyr. The downcore Fe<sub>R</sub>-OC contributes a relatively stable proportion of 13.3 ± 3.2% to TOC. However, distinctly lower values of less than 5% of TOC, accompanied by notable <sup>13</sup>C depletion of Fe<sub>R</sub>-OC, are observed in the sulfate-methane transition zone (SMTZ). Fe<sub>R</sub>-OC is suggested to be remobilized by microbially mediated reductive dissolution of Fe<sub>R</sub> and subsequently remineralized, the flux of which is 18-30% of the methane consumption in the SMTZ. The global reservoir of Fe<sub>R</sub>-OC in microbially active Quaternary marine sediments could be 19-46 times the size of the atmospheric carbon pool. Thus, the Fe<sub>R</sub>-OC pool may support subseafloor microorganisms and contribute to regulating Earth's carbon cycle.